Heating device for heating a moveable part of an automobile, especially a steering wheel heater

ABSTRACT

The invention relates to a heating device for a moveable part of a motor vehicle such as an automobile which can be held, such as a steering wheel. The heater is connected to a source of electrical energy in a stationary part of the vehicle by a contact unit having a stator and a rotor. A voltage converter of the heating device is provided in the stationary part of the vehicle, before the contact unit or in the stator of the contact unit. The voltage converter enables the generation of a higher voltage than the normal 12 volt standard voltage of the vehicle.

FIELD OF THE INVENTION

The invention relates to a heating device for heating a movable part ofa motor vehicle, more particularly a steering wheel heater.

BACKGROUND OF THE INVENTION

It is known to heat parts of a vehicle which can be held, moreparticularly the steering wheel. For example, a steering wheel with anelectric heater is known from DE 41 08 114 A1. There, a heat conductormade of copper wire is provided in the surface area of the steeringwheel cover and is connected to a power supply device in the vehicle bya switch mechanism. In conjunction with a thermo-sensor, this serves toswitch on the heater when required. From practice, it is known tooperate the heater with a voltage of 12 volts and a current strength of8 amps. As a result of this large current strength, it is standardpractice to transfer the current from the battery through a contact unitwith a slip ring/carbon brush to the steering wheel, because in the caseof transfer by means of a strip conductor, the latter is no longersufficiently flexible as a result of the minimum cross-section required,and because fewer conductors can be set in one contact unit and thusfewer consumers can be controlled.

SUMMARY OF THE INVENTION

The object of the invention is to supply the heating device withelectric energy through a sufficiently flexible strip conductor having across-section such as is usual for supplying the remaining consumers inthe steering wheel. The invention is a heating device for heating amovable part of a motor vehicle which can also be held, moreparticularly, a steering wheel heater which is connected through acontact unit having a stator and rotor to a source of electric energy inthe stationary part of the vehicle. According to the invention, avoltage converter for the heating device is mounted in the stationarypart of the vehicle in front of the contact unit or in the stator of thecontact unit to generate a voltage which is higher than the standard 12volt voltage in the vehicle. The voltage lies preferably between 35 and50 volts and more preferably amounts to 48 volts.

By increasing the voltage, it is possible to reduce the current strengthnecessary to achieve a predetermined heating output, and it is alsopossible to use flat strip conductors having such small cross-sectionsthat they are sufficiently flexible. Owing to the small cross sections,the number of flat strip conductors in the contact unit need not bereduced compared to an assembly without heater.

A DC/DC converter is preferably provided as the voltage converter.

It is furthermore expedient if the heating device is associated withcontrol electronics having a temperature sensor for observing thepredetermined maximum or minimum temperatures of the part which is to beheated.

DESCRIPTION OF THE DRAWINGS

The invention will now be explained with reference to one embodimentshown in the drawings in which:

FIG. 1 is a plan view of a section of a steering wheel;

FIG. 2 is a section II—II along FIG. 1:

FIG. 3 is a block circuit diagram for a heating device.

DETAILED DESCRIPTION

A heating device 2 with connecting leads 3, 4 is provided in the coverof a steering wheel 1. The heating device is associated with controlelectronics 5 and a temperature sensor 6. The connecting leads 3, 4 areconnected to the rotor 9 of a contact unit 7. Flat strip conductors 10run in a known way between the rotor 9 and a stator 8.

A DC/DC converter 12 is mounted between the stator 8 and the stationaryvoltage source (not shown) which has a voltage of 12 to 13.5 volts atits output, with the output of the converter being connected to thestator 8 by a supply lead 11. The DC/DC converter 12 transforms thevoltage to 48 volts. This exists at the input of the stator and allowsthe use of a flat strip conductor having a small cross-section, as isstandard for supplying the remaining consumers in the steering wheel,which are operated with a voltage of 12 volts, to be used also for theheater.

What is claimed is:
 1. A heating device for heating a movable part of amotor vehicle that has the movable part, a stationary part, and a sourceof electric energy including a motor vehicle battery in the stationarypart of the vehicle, the heating device comprising: a contact unithaving a stator and a rotor; a voltage converter located in thestationary part of the vehicle; and a heat conductor located in themovable part, wherein the heat conductor is connected to the source ofelectric energy through the contact unit and the voltage converter, andwherein the voltage converter generates a voltage higher than 12 volts.2. A heating device according to claim 1 wherein the voltage generatedis between 35 and 50 volts.
 3. A heating device according to claim 1wherein the voltage generated is 48 volts.
 4. A heating device accordingto claim 1 wherein the voltage converter is a DC/DC converter.
 5. Aheating device according to claim 1 further comprising controlelectronics having a temperature sensor to detect a predeterminedmaximum or minimum temperature of the movable part to be heated.
 6. Theheating device of claim 1 wherein the movable part is a steering wheel.7. The heating device of claim 1 further comprising strip conductorsbetween the stator and the rotor, wherein voltage is passed through thecontact unit by means of the strip conductors.
 8. A heating assembly fora motor vehicle comprising: a movable part configured to be held by anoccupant of the vehicle and a stationary part, a source of electricenergy including a motor vehicle battery in the stationary part, acontact unit having a stator connected to the stationary part and arotor connected to the movable part, a heat conductor in the movablepart connected to the source of electric energy in the stationary partof the vehicle through the contact unit and a voltage converter providedin the stationary part of the vehicle, located one of between the sourceof electric energy and the contact unit, and in the stator of thecontact unit, wherein the voltage converter generates a voltage higherthan 12 volts.
 9. A heating assembly according to claim 8 wherein thevoltage generated is between 35 and 50 volts.
 10. A heating assemblyaccording to claim 8 wherein the voltage generated is 48 volts.
 11. Aheating assembly according to claim 8 wherein the voltage converter is aDC/DC converter.
 12. A heating assembly according to claim 8 furthercomprising control electronics having a temperature sensor to detect apredetermined maximum or minimum temperature of the movable part to beheated.
 13. The heating assembly of claim 8 wherein the movable part isa steering wheel.
 14. The heating assembly of claim 8 further comprisingstrip conductors between the stator and the rotor, wherein voltage ispassed through the contact unit by means of the strip conductors.
 15. Aheating assembly for a motor vehicle, comprising: a movable part whichcan be held by an occupant of the vehicle and a stationary part, asource of electric energy including a motor vehicle battery in thestationary part having a specific voltage, a contact unit having astator connected to the stationary part and a rotor connected to themovable part, a heat conductor in the movable part connected to thesource of electric energy in the stationary part of the vehicle throughthe contact unit and a voltage converter provided in the stationary partof the vehicle, located one of between the source of electric energy andthe contact unit, and in the stator of the contact unit, wherein thevoltage converter generates a voltage higher than the specific voltageof the source of electric energy.
 16. A heating assembly according toclaim 15 wherein the voltage generated is between 35 and 50 volts.
 17. Aheating assembly according to claim 15 wherein the voltage converter isa DC/DC converter.
 18. A heating assembly according to claim 15 furthercomprising control electronics having a temperature sensor to detect apredetermined maximum or minimum temperature of the movable part to beheated.
 19. The heating assembly of claim 15 wherein the movable part isa steering wheel.
 20. The heating assembly of claim 15 furthercomprising strip conductors between the stator and the rotor, whereinvoltage is passed through the contact unit by means of the stripconductors.
 21. The heating device of claim 1 wherein the voltageconverter is located one of in front of the contact unit or in thestator of the contact unit.